Sustainable management of poultry manure: determination of biochemical methane potential (BMP) in probiotic-fed and commercial-fed broiler farms in Malaysia

Context Poultry industry contributes to major global greenhouse-gas (GHG) emissions, especially in manure management. However, the maximum methane (CH4) potential (B0) of broiler manure in Malaysia’s farm condition is still unknown. It was hypothesized that manure collected from contrasting broiler farm systems would differ in biochemical methane potential. Aims To determine the B0 of manure collected from four broiler farms representing contrasting feeding-regime and housing-system combinations in Malaysia, evaluated during the starter and grower phases, and to compare the measured values with the Intergovernmental Panel on Climage Change (IPCC) default. Methods Manure from the four farm systems, namely, probiotic-fed, high-rise (PH); probiotic-fed, deep-litter (PD); commercial-fed, high-rise (CH); commercial-fed, deep-litter (CD), was evaluated during the starter (S) and grower (G) phases by using standardized biochemical methane potential (BMP) assays conducted in triplicate in a laboratory to obtain B0. Triplicate 500 mL glass bottles were incubated anaerobically for 36 days in a laboratory. Biogas volume was measured daily; methane concentrations were analyzed with gas chromatography–thermal conductivity detector (GC–TCD). B0 was expressed as cubic meters of methane produced per kilogram of volatile solids (m3 CH4/kg VS). Key results Methane yield ranged from 14.60 to 138.17 mL CH4/g VS, whereas B0 ranged from 0.02 to 0.14 m3 CH4/kg VS. Among the sampled farms, manure from the probiotic-fed farms generally showed lower methane yields than did manure from the corresponding commercial-fed farms, and manure from the high-rise farms generally showed lower yields than did manure from the corresponding deep-litter farms. Grower-phase methane yield was lower than starter-phase yield in three of the four farms. These comparisons represent farm-specific observational patterns and cannot be attributed independently to feeding regime or housing system. All B0 values were substantially lower (62–96%) than the IPCC default (~0.36 m3 CH4/kg VS). Conclusions Methane potential differed among manure samples obtained from the four farm systems, with lower values generally observed in samples from the probiotic-fed and high-rise farms. Implications The four sampled farms differed substantially in manure methane potential. Lower methane yields were observed in the sampled probiotic-fed and high-rise farms, but these associations cannot be separated from other farm-specific characteristics. The measured B0 values were lower than the IPCC default, indicating the importance of further multi-farm studies to develop representative Malaysian emission factors.